Gauge control for a rolling mill



1959 v v .1. s. STRANGE:

GAUGE CONTROL FOR A ROLLING MILL Filed Feb. 25, 1967 Sheet of 2 FIG. I

INVEN'IO JOHN S. STRAN ATTORNEYS Jan. 21, 1969 J, 5. STRANGE GAUGE CONTROL FOR A ROLLING MILL Sheet 2 of 2 Filed Feb. 23, 1967 I12 INVENTOR. JOHN S. STRANGE IL, 744%, g M,

ATTORNEYS United States Patent 3,422,650 GAUGE CONTROL FOR A ROLLING MILL John Sherman Strance, Drexel Hill, Pa., assignor to E. W. Bliss Company, Canton, Ohio, a corporation of Delaware Filed Feb. 23, 1967, Ser. No. 618,093 US. Cl. 721

6 6 Claims Int. Cl. B21b 37/02; BZlb 31 32; F16c 7/04 ABSTRACT OF THE DISCLOSURE The present invention pertains to the art of rolling mills, and more particularly to a gauge control for rolling mills.

The invention is particularly applicable for a two-high rolling mill for reducing the thickness of a metal strip, and it will be described with particular reference thereto; however, it will \be appreciated that the invention has much broader applications and may be used in other rollin mills and similar apparatus.

In processing metal strip, it is normal practice to pass the strip successively through rolling mill stands having two working rolls adapted to engage the strip. These rolls decrease the thickness of the strip to the desired measurements. The rolls are generally supported in spaced chocks which are adjustable in a vertical direction to vary the spacing of the working rolls. Mechanical jacks or hydraulic devices are provided to perform the adjustment of the chocks; however, this arrangement presents a serious difficulty. The adjustment of the chocks is relatively coarse. For this reason, the chocks are adjusted only periodically. It has been found that this results in a strip which may have a varying thickness because of inherent changes in the rolling operation and the metallurgy of the strip. Consequently, it has become well known that the spacing of the rolls, especially during finish rolling of a strip, must be changed rapidly, and automatically, upon slight variations in the thickness, or gauge, of a strip issuing from the working rolls. One of the first systems for controlling the gauge of the strip included a means for sensing the thickness of the strip together with a means for adjusting the spacing of the chocks in accordance with gauge variations. This arrangement was not satisfactory. The normal chock adjusting mechanisms could not be accurately controlled to provide an accurate gauge. In addition, the time for making an adjustment of the distance between the chocks was so excessive that correction was not effected as rapidly as desired.

To overcome the disadvantages of the gauge control system mentioned above, it has been suggested that hydrodynamic bearings could be used between the necks of the working rolls and the cylindrical surfaces within the chocks. As the working rolls rotated, a hydrodynamic bearing action was created which would shift the working rolls downwardly against the strip being processed. A sensing device was then suggested for moving at least one of the working rolls in a horizontal direction to effect, somewhat, a vertical shifting of the working roll spacing. As the roll was shifted horizontally, the hydrodynamically created wedge of oil would cause a vertical displacement of the working rolls. Such a system is illustrated in United States Letters Patent 3,101,980. This particular system has not been adopted by the trade because it exhibits certain inherent disadvantages. For one this, this particular system requires longitudinal or horizontal movement of a working 3,422,650 Patented Jan. 21, 1969 roll to change the gauge of a processed strip. It is well known in the trade that such shifting of the working rolls can cause non-uniformity of strip thickness across the width of the strip. In addition, the spacing of the working rolls in the above-mentioned gauge control system is affected by the rotary speed of the working rolls. At zero speed, there is no hydrodynamic bearing action, and the working rolls will rest against a portion of the cylindrical supporting surface of the adjustable chocks. Also, this particular type of gauge control system is inherently dependent upon temperature of the liquid between the working roll necks and the chock surfaces, as well as the viscosity of this liquid. Consequently, as the rolling mill heats up during operation drastic changes are realized in the gauge control system.

All of these disadvantages are overcome by the present invention which is directed toward a gauge control for a rolling mill wherein hydrostatic pressure is introduced between the necks of the working rolls and the cylindrical surfaces of the chocks and the pressures around the cylindrical surfaces are adjusted to compensate for variations in the thickness of the strip issuing from the mill.

In accordance with the present invention, there is provided an improvement in a rolling mill comprising transversely spaced stands, two transversely extending, spaced working rolls with outer necks and generally cylindrical working surfaces through which a metal strip passes in a given path, chocks in the stands and having openings for journalling the necks, and means for moving the chocks with respect to each other for adjusting the gauge of the metal strip passing between the rolls. The improvement of the present invention comprises the provision of each opening defining a generally cylindrical surface and having a plurality of recesses in this surface. There is also provided means for forcing pressurized liquid into each of the recesses, at least one of the recesses being on the side of the surface opposite the strip, means for sensing variations in the gauge of the strip as it leaves the rolls, and means responsive to the sensing means for changing the pressure in one recess to control the gauge of the strip.

The primary object of the present invention is the provision of a gauge control system for a rolling mill including spaced working rolls with journal necks, which system uses hydrostatic liquid pressure to support the rolls and change the spacing therebetween.

Another object of the present invention is the provision of a gauge control system for a rolling mill including spaced working rolls with journal necks which system can be used with existing equipment with a minimum of modification.

Still another object of the present invention is the provision of a gauge control system for a rolling mill including spaced working rolls with journal necks which system allows larger roll neck diameters than heretofore possible.

Still a further object of the present invention is the provision of a system as defined above which is not affected detrimentally by changes in liquid viscosity, operating temperatures and roll speeds.

These and other objects and advantages will become apparent from the following description used to illustrate the preferred embodiments of the invention as read in connection with the accompanying drawings in which:

FIGURE 1 is a front plan view showing, somewhat schematically, the environment to which the present invention is directed;

FIGURE 2 is an enlarged cross-sectional view illustrating, somewhat schematically, one aspect of the present invention;

FIGURE 3 illustrating, somewhat schematically, bodiment of the present invention;

is an enlarged, partial, cross-sectional view the preferred em- FIGURE 4 is a partially cross-sectioned view illustrating another aspect of the present invention; and,

FIGURE 5 is a view, similar to FIGURE 3, illustrating, somewhat schematically, another modification of the preferred embodiment of the present invention.

Referring now to the drawing wherein the showings are for the purpose of illustrating preferred embodiments of the invention only and not for the purpose of limiting same, FIGURE 1 shows a two-high rolling mill A for processing a metal strip B. The mill, as is standard practice, includes two transversely spaced stands 10, 12 for supporting vertically spaced working rolls 14, 16, each of which has outwardly extending necks 18. These necks are rotatably mounted within chocks 20, 22 so that drive shafts 24, 26 can rotate the working rolls at the desired speed. Jacks 30 having downwardly extending screws 32 are adapted to vertically adjust chocks 20. In a like manner, screws 34 adjust the lower chocks 22. These structures are best illustrated in FIGURE 2. The jacks are used for coarse adjustment of the spacing of the working roll; however, during operation relatively fine adjustment of the spacing must be made so that the gauge of the strip B remains somewhat constant. The present invention is directed toward an automatic control for maintaining this relatively constant gauge for the strip.

Referring now to the roll 14 and chocks 20, as shown in FIGURES 24, the chocks include an inner cylindrical surface 40, and the roll neck includes an outer surface 42. These surfaces may have somewhat the same diameter; however, relative movement is required so the diameter of surface 42 is smaller than the diameter of surface 40. In accordance with the present invention, the surface 40 is provided with a plurality of recesses which are arranged in axially spaced pairs. As best shown in FI URES 3 and 4, upper recesses 44, 46 are defined between lands 48, 49. Lower recesses 50, 52 are defined between lands 51, 53. In a like manner there are provided axially spaced side recesses 54, 56, only one of which is shown on each side of the chocks. These side recesses are defined by circumferentially spaced lands 58, 59. As shown in FIGURE 4, annular recesses 60, 62 are provided around the complete surface 40, and these recesses form return lines for liquid which is pumped under pressure to the various recesses. These annular recesses are provided with continuous lands 68, 69 to prevent outflow of liquid. Seals 64, 66 are provided to assist in the prevention of liquid outflow from the chocks.

The upper recesses are provided with independent passages 70, 72 While the lower recesses are provided with separate passages 74, 76. In a like manner, each of the side recesses 54, 56 are provided with dual, separate passages 80, 82, respectively. Referring now to FIGURE 2, a sensing unit 90 is provided for sensing the thickness of strip B as it issues from the mill. The sensing unit is directly connected to and controls variable pressure pumps 92, 94. Of course, flow control valves could be used to control the flow of liquid from the pumps to change the supporting liquid flow. A relatively constant pressure pump 96 is also illustrated. The pumps 92, 94, or control valves therefor, are controlled to increase the pressure and flow of liquid within the upper recesses when the sensing device 90 indicates an increase in the gauge of the strip. Conversely, when the sensing unit indicates a decrease in the thickness of the strip, the pumps 92, 94 are caused to automatically reduce the pressure and flow of liquid being applied through passages 70, 72 to the recesses 44, 46, respectively. In this manner, the gauge of the strip is automatically controlled without relying upon the speed of the rolls or longitudinal movement of the rolls with respect to each other.

Referring now to FIGURE 3, the upper recesses 44, 46, and their lands 48, 49 have an annular length of at least approximately 120. It has been found that with a pressure less than 500 pounds per square inch and a maximum rolling force of 1.6 million pounds the length of the upper recesses should approach at least 120. The width of the lands 48, 49 is relatively small; therefore, they can be included in this length.

By providing axially spaced recesses, there is less tendency for deforming the working roll during gauge control operation. Referrin to FIGURE 4, the diameter of roll 14 is represented by a and the diameter of neck 18 is represented by b. If the roll is to be removed transversely from the stand 12, the diameter of roll 14 must be less than the opening 12. This is not illustrated in FIGURE 2; however, it is somewhat common practice. Since the roll diameter is determined by the size of opening 12', it has been found, in the past, that the diameter of neck 18 had to be approximately .7.8 times the size of the roll so that appropriate anti-friction bearings could be provided within the chocks. By utilizing the present invention, a relatively thin layer of liquid, such as oil, is used as a bearing; therefore, the dimension b can be up to 95% of the dimension a. The only limitation is that the dimension a must be greater than the dimension b to provide sufiicient material for a subsequent regrinding of the roll 14. Consequently, by utilizing the present invention a relatively larger neck may be provided. This increases the rigidity of the working roll. It has been found that a roll having a diameter of 36 inches could be provided with a neck of 34 inches by using the present invention. In other words, the ratio of b to a may be increased to approximately 95 Referring now to FIGURE 5, a second embodiment of the invention is illustrated. In this embodiment the inner surface of the chocks include two upper blocks 100, 102 provided with recesses 104, 106, respectively. Each of the blocks has a circumferential length of approximately 60 or more. This provides an upper support of approximately or more. Lower blocks 110, 112 are also provided and have recesses 114, 116. It is appreciated that only one set of recesses is illustrated; however, these recesses are provided in pairs, as previously explained. Appropriate pressure is introduced into the upper recesses to control the gauge of strip passing between the working rolls, in a manner previously described. It is also appreciated that gauge control may be effected by changing the pressure of the roller recesses in the illustrated embodiments of the invention. It is within the preferred embodiment of the present invention that the pressure within side recesses of the bearing structure is maintained in a somewhat balanced condition so that the working rolls are not moved longitudinally during operation of the mill A.

The present invention has been described in connection with certain schematically illustrated embodiments; however, it should be appreciated that various changes may be made in these embodiments without departing from the intended spirit and scope of the present invention as defined in the appended claims.

Having thus described my invention, I claim:

1. In a rolling mill comprising transversely spaced stands, two transversely extending, spaced working rolls with outer necks and generally cylindrical working surfaces between which a metal strip passes in :a given path, chocks in said stands having openings for journalling said necks, and means for moving said chocks with respect to each other for adjusting the gauge of the metal strip passing between said rolls, the improvement comprising: each of said openings defining a generally cylindrical surface, a plurality of recesses in said surface, means for forcing pressurized liquid into each of said recesses, at least one of said recesses being on the side of said surface opposite said strip, means for sensing variations in the gauge of said strip as it leaves said rolls, and means responsive to said sensing means for changing the pressure in said one recess to control the gauge of said strip.

2. The improvement as defined in claim 1 wherein two of said recesses are provided on the side of said surface opposite said strip, and said responsive means controlling pressure in said two recesses.

3. The improvement as defined in claim 2 wherein said recesses are spaced circumferentially on said surface.

4. The improvement as defined in claim 2 wherein said recesses are spaced axially.

5. The improvement as defined in claim 1 wherein said one recess extends circumferentially around said surface at least approximately 120.

6. The improvement as defined in claim 1 including two side recesses in each of said surfaces, said side recesses being generally diametrically opposed, and means for applying generally constant pressure to said side recesses to prevent longitudinal movement of said rolls.

References Cited UNITED STATES PATENTS U.S. Cl. X.R. 

